The invention relates generally to audio control systems and more particularly to computer based audio control systems for multichannel audio surround sound systems.
With the proposal of increased video and audio applications in multimedia personal computers, a user can potentially use the computer to control the television, telephone and home stereo as well as connect signals from cable television links, satellite TV and various other video/audio sources such as compact disc (CD) players, VCRs and digital versatile disc (DVD) players to the home entertainment system.
Some high-end home entertainment systems have multichannel audio systems, such as surround sound systems with three or more channels to provide theater sound effects. The surround sound channels are often presented at a lower volume level than front channels since movies contain most of the audio information in the front channels and use the surround channels sparingly as effects channels. A typical surround multichannel system may include six channels. These channels typically consist of a left, right and center front channel, a left and right surround channel and a subwoofer channel. Differing prerecorded equalization settings among surround channel recording or among the various formats can sound different on the same speakers.
The first surround systems sold to consumers were generally meant for playback of surround sound movies. These movie sound tracks typically had an uneven distribution of information to the six speakers in the system. Because of this, many surround sound systems exist with unmatched speakers. In other words each speaker has its own physical limitations corresponding to the information expected in that channel. However, for multi-channel music, an even distribution of audio information is expected in each channel. For example, in a movie soundtrack, the low frequency or subwoofer channel typically carries all the low frequency information. Typically this means that all other channels will have a minimum of low frequency information and as such the remaining five speakers are not required to provide quality low frequency output. The center channel typically carries mostly dialog, with some residual effects information and some music information. The speaker corresponding to the center channel is usually limited to playback in the vocal frequency range and can provide more energy than left and right and speakers and surround left and right surround channel speakers. The left and right channels typically carry most of the music soundtrack, and as such, the corresponding speakers have a wide frequency range. The left and right surround channels usually carry only sound effects and are therefore generally limited in frequency range and in power. Accordingly, speakers used for left and right surround channels typically have limited frequency ranges and power ranges.
A problem can arise for multi-channel music since the left, center, right, left surround and right surround speakers can all carry music and are expected to be matched and capable of handling the full range of frequencies. In fact, some multi-channel music mixes do not use the subwoofer as it has been known to artificially boost the low frequencies. Therefore each of the remaining five speakers are expected to handle the low frequency energy as well as the mid range and higher frequencies. Purchasing a new set of matching speakers to take further advantage of the newer multi-channel music recordings is unnecessarily costly. Moreover, it would be advantageous to have a flexible audio system that could automatically compensate for speaker limitations with minimal user intervention.
Some automatic equalization systems are known that may automatically generate filter coefficients and delay parameters to compensate for physical limitations of an audio playback system. Such systems are typically for use in concert halls and professional recording studios. With such systems, the operator typically needs to know details about complex variables including room attenuation parameters, speaker response characteristics and other information which is not generally known to average consumers. Moreover such systems are typically very costly and do not lend themselves to mass market use. Accordingly, it would be desirable to have a automatic channel balancing and room tuning system that may be used on a multimedia computer system or other consumer data processing systems for enhancing multi-channel audio surround sound systems.
In addition to the unmatched speakers, the nature of the room in which the speakers are placed will also affect the sound. As is known, sound reflects off certain surfaces and may be absorbed by other surfaces. Some surfaces diffuse audio signals, causing some frequencies to be canceled out. Other frequencies may resonate if the wave length of the frequency and the dimensions of the room are matched. It would be desirable if a lower cost surround sound channel system were able to compensate to reduce the more offensive resonances and cancellations.
Therefore a need exists for an automatic channel balancing method and system to help maximize performance of surround sound systems. Such a system should automatically compensate for the physical limitations of the room and differing response characteristics of the speakers in the surround sound system.